Investigation of Synergistic Influence of Ultrasound and Co-Doping to Degrade Toluene from Polluted Air in Construction Sites—An Experimental Approach

Background: Toluene exposure in construction workers can lead to several health problems, primarily affecting the nervous system, respiratory system, and skin. Utilizing advanced photocatalytic materials to degrade gaseous toluene aims to significantly mitigate its negative impact. Methods: In this research, photocatalysts based on pure TiO2 and modified TiO2 were synthesized to evaluate their efficacy in degrading gaseous toluene, a prevalent air pollutant in construction settings. Two synthesis methods were employed. Sonoprecipitation was used to create Fe-N co-doped TiO2 nanoparticles in the first method, while the second method utilized co-precipitation and hydrothermal techniques without ultrasonic assistance to achieve Fe-N co-doping. Seven types of nanophotocatalysts were synthesized, including TiO2-U (with ultrasonic assistance), NTiO2-U, FeNTiO2 (2.5)-U, FeNTiO2 (5)-U, FeNTiO2 (7.5)-U, FeNTiO2 (10)-U, and FeNTiO2 (5) without ultrasonic assistance. Characterization of the synthesized photocatalysts involved various analyses, including XRD, SEM, EDX, UV–VIS DRS, FT–IR, BET, and N2 adsorption-desorption isotherm. Results: Ultrasonic assistance notably improved particle dispersion and prevented agglomeration on the photocatalyst surface. UV–VIS DRS analysis indicated a reduction in band gap energy due to Fe and N doping of TiO2. The study also investigated the influence of Fe doping, initial toluene concentration, light source, and residence time on the degradation rate of gaseous toluene. Experimental findings showed that FeNTiO2 (5)-U exhibited a higher degradation rate of toluene (63.5%) compared to FeNTiO2 (5) (50%) under visible light irradiation over 15 s. Conclusions: The study underscores the significant enhancement in photocatalytic activity for toluene degradation achieved through the combined effects of ultrasound and co-doping methods.